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Self Calibration of Motion and Stereo Vision for Mobile RobotsNavigation - Brooks, Rodney A.; Flynn, Anita M.; Marill, Thomas
We report on experiments with a mobile robot using one vision process (forward motion vision) to calibrate another (stereo vision) without resorting to any external units of measurement. Both are calibrated to a velocity dependent coordinate system which is natural to the task of obstacle avoidance. The foundations of these algorithms, in a world of perfect measurement, are quite elementary. The contribution of this work is to make them noise tolerant while remaining simple computationally. Both the algorithms and the calibration procedure are easy to implement and have shallow computational depth, making them (1) run at reasonable speed on moderate...
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Obviously Synchronizable Series Expressions: Part I: User's Manual for the OSS Macro Package - Waters, Richard C.
The benefits of programming in a functional style are well known. In particular, algorithms that are expressed as compositions of functions operating on series/vectors/streams of data elements are much easier to understand and modify than equivalent algorithms expressed as loops. Unfortunately, many programmers hesitate to use series expressions, because they are typically implemented very inefficiently. Common Lisp macro packages (OSS) has been implemented which supports a restricted class of series expressions, obviously synchronizable series expressions, which can be evaluated very efficiently by automatically converting them into loops. Using this macro package, programmers can obtain the advantages of expressing computations as...
3.
Motion Field and Optical Flow: Qualitative Properties - Verri, Alessandro; Poggio, Tomaso
In this paper we show that the optical flow, a 2D field that can be associated with the variation of the image brightness pattern, and the 2D motion field, the projection on the image plane of the 3D velocity field of a moving scene, are in general different, unless very special conditions are satisfied. The optical flow, therefore, is ill-suited for computing structure from motion and for reconstructing the 3D velocity field, problems that require an accurate estimate of the 2D motion field. We then suggest a different use of the optical flow. We argue that stable qualitative properties of...
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Stereo and Eye Movement - Geiger, Davi; Yuille, Alan
We describe a method to solve the stereo correspondence using controlled eye (or camera) movements. These eye movements essentially supply additional image frames which can be used to constrain the stereo matching. Because the eye movements are small, traditional methods of stereo with multiple frames will not work. We develop an alternative approach using a systematic analysis to define a probability distribution for the errors. Our matching strategy then matches the most probable points first, thereby reducing the ambiguity for the remaining matches. We demonstrate this algorithm with several examples.
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The Analysis of Visual Motion: From Computational Theory to Neuronal Mechanisms - Hildreth, Ellen C.; Koch, Christof
This paper reviews a number of aspects of visual motion analysis in biological systems from a computational perspective. We illustrate the kinds of insights that have been gained through computational studies and how these observations can be integrated with experimental studies from psychology and the neurosciences to understand the particular computations used by biological systems to analyze motion. The particular areas of motion analysis that we discuss include early motion detection and measurement, the optical flow computation, motion correspondence, the detection of motion discontinuities, and the recovery of three-dimensional structure from motion.
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Regularization Theory and Shape Constraints - Verri, Alessandro; Poggio, Tomaso
Many problems of early vision are ill-posed; to recover unique stable solutions regularization techniques can be used. These techniques lead to meaningful results, provided that solutions belong to suitable compact sets. Often some additional constraints on the shape or the behavior of the possible solutions are available. This note discusses which of these constraints can be embedded in the classic theory of regularization and how, in order to improve the quality of the recovered solution. Connections with mathematical programming techniques are also discussed. As a conclusion, regularization of early vision problems may be improved by the use of some constraints...
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Visual Attention in Brains and Computers - Hurlbert, Anya; Poggio, Tomaso
Existing computer programs designed to perform visual recognition of objects suffer from a basic weakness: the inability to spotlight regions in the image that potentially correspond to objects of interest. The brain's mechanisms of visual attention, elucidated by psychophysicists and neurophysiologists, may suggest a solution to the computer's problem of object recognition.
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Computations in the Vertebrate Retina: Gain Enhancement, Differentiation and Motion Discrimination - Koch, Christof; Poggio, Tomaso; Torre, Vincent
The vertebrate retina, which provides the visual input to the brain and its main interface with the outside world, is a very attractive model system for approaching the question of the information processing role of biological mechanisms of nerve cells. It is as yet impossible to provide a complete circuit diagram of the retina, but it is now possible to identify a few simple computations that the retina performs and to relate them to specific biophysical mechanisms and circuit elements. In this paper we consider three operations carried out by most retinae: amplification, temporal differentiation, and computation of the direction...
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Toward a Requirements Apprentice: On the Boundary Between Informal and Formal Specifications - Rich, Charles; Waters, Richard C.
Requirements acquisition is one of the most important and least well supported parts of the software development process. The Requirements Apprentice (RA) will assist a human analyst in the creation and modification of software requirements. Unlike current requirements analysis tools, which assume a formal description language, the focus of the RA is on the boundary between informal and formal specifications. The RA is intended to support the earliest phases of creating a requirement, in which incompleteness, ambiguity, and contradiction are inevitable features. From an artificial intelligence perspective, the central problem the RA faces is one of knowledge acquisition. It has...
10.
Boolean Classes - McAllester, David; Zabih, Ramin
Object-oriented programming languages all involve the notions of class and object. We extend the notion of class so that any Boolean combination of classes is also a class. Boolean classes allow greater precision and conciseness in naming the class of objects governed by a particular method. A class can be viewed as a predicate which is either true or false of any given object. Unlike predicates however classes have an inheritance hierarchy which is known at compile time. Boolean classes extend the notion of class, making classes more like predicates, while preserving the compile time computable inheritance hierarchy.
11.
Massively Parallel Implementations of Theories for Apparent Motion - Grzywacz, Norberto; Yuille, Alan
We investigate two ways of solving the correspondence problem for motion using the assumptions of minimal mapping and rigidity. Massively parallel analog networks are designed to implement these theories. Their effectiveness is demonstrated with mathematical proofs and computer simulations. We discuss relevant psychophysical experiments.
12.
A Fully Abstract Semantics for Event-Based Simulation - Hall, Robert J.
This paper shows that, provided circuits contain no zero-delay loops, a tight relationship, full abstraction, exists between a natural event-based operational semantics for circuits and a natural denotational semantics for circuits based on causal functions on value timelines. The paper also discusses what goes wrong if zero-delay loops are allowed, and illustrates the application of this semantic relationship to modeling questions.
13.
Using Program Transformation to Improve Program Translation - Kennedy, Thomas R., III
Direct, construct by construct translation from one high level language to another often produces convoluted, unnatural, and unreadable results, particularly when the source and target languages support different models of programming. A more readable and natural translation can be obtained by augmenting the translator with a program transformation system.
14.
A Multiple Representation Approach to Understanding the Time Behavior of Digital Circuits - Hall, Robert J.; Lathrop, Richard H.; Kirk, Robert S.
We put forth a multiple representation approach to deriving the behavioral model of a digital circuit automatically from its structure and the behavioral simulation models of its components. One representation supports temporal reasoning for composition and amplification, another supports simulation and a third helps to partition the translation problem. A working prototype, FUNSTRUX, is described.
15.
Interaction of Different Modules in Depth Perception: Stereo and Shading - Bulthoff, Heinrich H.; Mallot, Hanspeter A.
A method has been developed to measure the perceived depth of computer generated images of simple solid objects. Computer graphic techniques allow for independent control of different depth queues (stereo, shading, and texture) and enable the investigator thereby to study psychophysically the interaction of modules for depth perception. Accumulation of information from shading and stereo and vetoing of depth from shading by edge information have been found. Cooperativity and other types of interactions are discussed. If intensity edges are missing, as in a smooth-shaded surface, the image intensities themselves could be used for stereo matching. The results are compared with...
16.
Ill-Posed Problems in Early Vision - Bertero, Mario; Poggio, Tomaso; Torre, Vincent
The first processing stage in computational vision, also called early vision, consists in decoding 2D images in terms of properties of 3D surfaces. Early vision includes problems such as the recovery of motion and optical flow, shape from shading, surface interpolation, and edge detection. These are inverse problems, which are often ill-posed or ill-conditioned. We review here the relevant mathematical results on ill-posed and ill-conditioned problems and introduce the formal aspects of regularization theory in the linear and non-linear case. More general stochastic regularization methods are also introduced. Specific topics in early vision and their regularization are then analyzed rigorously,...
17.
Parallel Algorithms for Computer Vision on the Connection Machine - Little, James J.
The Connection Machine is a fine-grained parallel computer having up to 64K processors. It supports both local communication among the processors, which are situated in a two-dimensional mesh, and high-bandwidth communication among processors at arbitrary locations, using a message-passing network. We present solutions to a set of Image Understanding problems for the Connection Machine. These problems were proposed by DARPA to evaluate architectures for Image Understanding systems, and are intended to comprise a representative sample of fundamental procedures to be used in Image Understanding. The solutions on the Connection Machine embody general methods for filtering images, determining connectivity among image...
18.
Functional Abstraction From Structure in VLSI Simulation Models - Lathrop, Richard H.; Robert J. Hall,; Kirk, Robert S.
High-level functional (or behavioral) simulation models are difficult, time-consuming, and expensive to develop. We report on a method for automatically generating the program code for a high-level functional simulation model. The high-level model is produced directly from the program code for the circuit components' functional models and a netlist description of their connectivity. A prototype has been implemented in LISP for the SIMMER functional simulator.
19.
On Dynamic Models of Robot Force Control - Eppinger, Steven D.; Seering, Warren P.
For precise robot control, endpoint compliance strategies utilize feedback from a force sensor located near the tool/workpiece interface. Such endpoint force control systems have been observed in the laboratory to be limited to unsatisfactory closed-loop performance. This paper discusses the particular dynamic properties of robot systems which can lead to instability and limit performance. A series of lumped-parameter models is developed in an effort to predict the closed-loop dynamics of a force-controlled single axis arm. The models include some effects of robot structural dynamics, sensor compliance, and workpiece dynamics. The qualitative analysis shows that the robot dynamics contribute to force-controlled...
20.
The Revised Revised Report on Scheme or An Uncommon Lisp - Clinger, William
Data and procedures and the values they amass, Higher-order functions to combine and mix and match, Objects with their local state, the message they pass, A property, a package, the control of point for a catch- In the Lambda Order they are all first-class. One thing to name them all, one things to define them, one thing to place them in environments and bind them, in the Lambda Order they are all first-class. Keywords: SCHEME, LISP, functional programming, computer languages.
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